Conventionally, there is known a plasma processing apparatus which performs a processing, e.g., etching on a processing target substrate by using plasma. In such a plasma processing apparatus, the processing target substrate is placed on a mounting table which is provided within a chamber, and a processing gas is supplied into the chamber. Then, by applying a high frequency power into the chamber from an upper electrode which is disposed above the processing target substrate to face the processing target substrate on the mounting table, plasma of the processing gas is generated within the chamber. A preset plasma processing such as etching is performed on a surface of the processing target substrate by ions or radicals in the plasma. A negative DC voltage may be applied to the upper electrode.
Further, there is also known a plasma processing apparatus in which a ring-shaped conductive member, which is insulated from the upper electrode, is provided around the upper electrode (see, for example, Patent Document 1). A negative DC voltage having a magnitude different from that of the negative DC voltage applied to the upper electrode is applied to the conductive member.
Patent Document 1: Japanese Patent Laid-open Publication No. 2015-005755
In the plasma processing apparatus, a focus ring is provided around the mounting table to surround the processing target substrate placed on the mounting table. The focus ring is configured to improve uniformity of the plasma process such as etching which is performed on the processing target substrate. If, however, the plasma process is performed repeatedly in the plasma processing apparatus, the focus ring is consumed (worn). If the focus ring is consumed, the shape of the focus ring is changed, and so that a height relationship between a plasma sheath formed above the focus ring and a plasma sheath formed above the processing target substrate is changed. For this reason, the consumption of the focus ring causes a change in inclination angle of particles such as ions in the plasma when they reach the processing target substrate.
If the change in the inclination angle of the particles such as the ions in the plasma when they reach the processing target substrate is increased caused by the consumption of the focus ring, it may be difficult to suppress non-uniformity in inclination of a hole, which is formed on the processing target substrate, within a preset specification. Thus, the focus ring needs to be replaced before the non-uniformity in the inclination of the hole exceeds the preset specification. If the focus ring is replaced frequently, however, the process may be stopped whenever the focus ring is replaced, so that a throughput of the process is reduced.